Full Composition Range Research Articles

Excess enthalpy, density, speed of sound and refractive index of binary mixtures {2-(2-ethoxyethoxy)ethanol + 1-hexene, or cyclohexane, or methylcyclohexane at (298.15 and 313.15) K: Application of the PPR-78 cubic equation of state, NRTL and UNIQUAC models

Excess enthalpy, HE, density, ρ, speed of sound, u, and refractive index, nD, measured data (312 points) are presented for {2-(2-ethoxyethoxy)ethanol (carbitol) with 1-hexene, or cyclohexane, or methylcyclohexane} at 0.1 MPa and (298.15 and 313.15) K throughout the full range of composition. Consequently, derivative properties were determined from the reported experimental data: VE, excess volume, Ks, isentropic compressibility, ΔKs, deviation in isentropic compressibility, ΔnD, deviation in refractive index. The modified Redlich-Kister is employed for the experimental data correlation of HE, while the Predictive Peng-Robinson 1978 (PPR78) EoS is used to model the measured data of HE. As a comparison with PPR78 EoS, the NRTL and UNIQUAC models are applied to have a prediction on the experimental HE data. Also, the Redlich-Kister equation is employed to fit the excess volume, deviation in isentropic compressibility and deviation in refractive index. In the present work, we have discussed intermolecular interactions for the studied binary mixtures.

Analytic description of grain boundary segregation, tension, and formation energy in the copper–nickel system

In this theoretical study, a recently proposed segregation model is applied to segregation data of an exemplary Σ5 grain boundary (GB), which is investigated using a copper–nickel embedded-atom method potential. Segregation in the semi-grandcanonical ensemble is systematically studied by varying the chemical potential in order to explore the full composition range for temperatures from 500 K to 1000 K. As a major thermodynamic feature, the mentioned segregation model avoids the usage of interface compositions, for which an arbitrary volume must be defined, but rather models the thermodynamically unambiguous solute excess. It was shown that the solute excess and the interface formation energy could be described very accurately over a wide range of temperatures and over the entire composition range based on a composition-dependent, but temperature-independent effective energy of segregation. However, the model was initially derived for systems without lattice mismatch so that interface tensions were neglected. Since the copper–nickel system exhibits a moderate lattice mismatch of roughly 2.7%, the copper–nickel system is chosen in this study to further extend the segregation model by a linear-elastic theory to also account for the interface tensions. Using this extended model, it will be shown that the solute excess, GB tensions, and GB formation energies can be derived from the effective energy of segregation for all temperatures and over the whole composition range. As in principle only one single segregation isotherm is sufficient to determine the effective energy of segregation and derived thermodynamic interface quantities, the application of this model is especially interesting for experimental evaluations.

Full-composition-range glass transition behavior of the polymer/solvent system poly (lactic acid) / ethyl butylacetylaminopropionate (PLA/IR3535®)

The polymer/solvent system poly (lactic acid)/ethyl butylacetylaminopropionate (PLA/IR3535®) is considered as a drug-delivery system, in which a polymer hosts a liquid with a functionality as insect repellent. Such devices require solubility of the components at high temperature and observation of crystallization-induced solid-liquid phase separation on cooling. Precise knowledge of the thermodynamic solubility of the components is then difficult to obtain due to possible superposition of liquid-liquid phase separation with polymer crystallization. Therefore, in the present study the miscibility of the polymer/solvent system PLA/IR3535® was explored by employing non-crystallizable PLA, by analysis of the glass transition behavior in the full composition range. The data revealed that the two components are miscible regardless the system composition, with the glass transition temperature of solutions showing a negative deviation from the linear mixing rule, suggesting rather weak enthalpic interactions of the system components. The study included application of conventional and fast scanning chip calorimetry, which allowed for controlled and stepwise evaporation of solvent by repeated exposing the system to elevated temperature and evaluation of the glass transition temperature during in-between cooling and reheating. This novel approach permits an efficient analysis of the glass transition temperature as function of the system composition in a single experiment in a wide range of solvent concentrations.

The lattice parameter – composition relationship of the body centered cubic uranium-niobium alloys

In-situ time-of-flight neutron diffraction experiments were performed on uranium-niobium alloy with 6 wt% Nb to study the lattice parameter-composition relationship for the body centered cubic (bcc) alloys. Based on lattice-parameter measurements of Nb-supersaturated γs phase over the range of 450 – 790 °C, an improved Vegard's-type relationship was established for determination of Nb concentrations at elevated temperatures. Neutron diffraction data were also collected as a function of aging time over the 450 - 600 °C range when γs phase decomposed isothermally into the mixture of orthorhombic α-U and Nb-rich bcc phase, as well as at room-temperature on the alloys aged ex-situ at 500 °C up to five years. From these measurements, the average Nb concentrations in the bcc phase were determined based on the Rietveld refinements of weight fraction and mass conservation relations (lever rule). Over the 15at% – 78at% range of Nb concentrations that correspond to different experimental aging times, the lattice parameters at constant temperatures exhibit a nonlinear S-shaped variation with Nb concentration, and the associated excess volumes of mixing can be described by a subregular solution model of the Redlich–Kister type of polynomial. Over the full range of composition the S-shaped deviation from Vegard's law can be modeled using a combination of an elastic continuum model and a perturbation to the radii of the solute atoms in the solvent, suggesting that electronic interactions between solute and solvent atoms could play an important role in the compositional dependence of lattice parameter for the γ-phase U-Nb alloys. While Vegard's law is a straightforward and reasonably good approximation for the bcc solid solutions in the U-Nb system, the Nb concentrations determined from the weight fraction refinements of diffraction data provide internally consistent, mass-conserving estimates of solute redistribution for the monotectoid reaction.

High-Pressure Volumetric Properties of the Binary Mixtures (Di-isopropyl Ether + n-Heptane or Methylcyclohexane)

This work reports the experimental density data for the binary mixtures of n-heptane or methylcyclohexane + di-isopropyl ether, measured over the full composition range between 0.1 and 140 MPa, and...

Viscosity of magmatic melts: Improved structural - chemical model

Viscosity of magmatic melts is a key physical property that controls a variety of processes such as magma crystallization and differentiation, ascent and eruptions dynamics. Therefore, the physical-chemical model of forecasts and calculations of viscosity of magmatic melts is an actual problem of petrology and geochemistry. Here we present a unique model that for the first time allows reliable prediction of the viscosity of near-liquid magmatic melts in a full range of composition and conditions with high accuracy of the prediction (±30% rel. for viscosity, and ±1.0% rel. for activation energy). The new model is an advanced version of the model proposed earlier. The basic equation used in this model to calculate the composition, temperature, pressure, and phase dependences of the viscosity of magmatic melts is a partly modified Arrhenian equation:ηPT=ηoexpEXP/RTwhere ηo is the pre-exponential factor for the viscosity of melts at T → ∞, (ηo = 10–4.5 ± 10–0.1 Pa s); ηTP is the melt viscosity at given temperature, pressure and a volume content of crystals and bubbles in the melt (Pa s); T is the absolute temperature in K; EXP is the activation energy of viscous flow (J/mol) depending on melt composition, including volatile components, and pressure; R = 8.3192 (J/mol K) is the gas constant.This model predicts the viscosity of near-liquid silicate and magmatic melts over nine orders of magnitude of viscosity (10−1-108 Pa s) and transforms about 3 decades of experimental study of silicate and magmatic melt viscosities.

Influence of palatability on the feeding preferences of the endemic Hawaiian tiger cowrie for indigenous and introduced sponges

Kāne‘ohe Bay has been invaded by at least 10 non-indigenous sponge species, some of which have become dominant over native sponges and even competitors against reef-building corals. We discovered the Hawaiian tiger cowrieCypraea tigris schilderianato be a voracious sponge predator, particularly on some of these non-indigenous sponges. This study sought to examine whether feeding preference for sponges by cowries was influenced by palatability of sponge chemical extracts. We quantified the consumption rate of 18 species of common native and non-native sponges in comparison to 3 native corals from Kāne‘ohe Bay in flow-through aquaria. When offered a smorgasbord of prey species in 4 replicate week-long trials, cowries exclusively fed on sponges, which included several non-native species, in a selective gradient. ThreeDysideaspp. were consumed entirely within 72 h, followed byMycale parishii,Haliclona caerulea,Halichondria coerulea, andCladocroce buraphawithin 96 h, andM. grandisandGelliodes wilsoniin 144 h. Preferred sponges spanned the full range of sponge mineral composition, from those with densely packed spicules that measured >300 µm to those with a collagen fiber skeleton. Among avoided sponges, onlyMonanchora clathrataproduced compounds that, when extracted, proved to be a deterrent to cowries and the whitespotted tobyCanthigaster jactatorin feeding trials. Our study highlights the previously unrecognized importance of cowrie predation on introduced sponges in Hawaiian reefs, and suggests that palatability alone does not influence feeding preference. We encourage conservation for this overharvested, native spongivore because of its potential use in biological control for future sponge introductions.

Anomalies in Bulk Ion Transport in the Solid Solutions of Li7La3M2O12 (M = Hf, Sn) and Li5La3Ta2O12.

Cubic Li7La3Zr2O12(LLZO), stabilized by supervalent cations, is one of the most promising oxide electrolyte to realize inherently safe all-solid-state batteries. It is of great interest to evaluate the strategy of supervalent stabilization in similar compounds and to describe its effect on ionic bulk conductivity σ′bulk. Here, we synthesized solid solutions of Li7–xLa3M2–xTaxO12 with M = Hf, Sn over the full compositional range (x = 0, 0.25...2). It turned out that Ta contents at x of 0.25 (M = Hf, LLHTO) and 0.5 (M = Sn, LLSTO) are necessary to yield phase pure cubic Li7–xLa3M2–xTaxO12. The maximum in total conductivity for LLHTO (2 × 10–4 S cm–1) is achieved for x = 1.0; the associated activation energy is 0.46 eV. At x = 0.5 and x = 1.0, we observe two conductivity anomalies that are qualitatively in agreement with the rule of Meyer and Neldel. For LLSTO, at x = 0.75 the conductivity σ′bulk turned out to be 7.94 × 10–5 S cm–1 (0.46 eV); the almost monotonic decrease of ion bulk conductivity from x = 0.75 to x = 2 in this series is in line with Meyer–Neldel’s compensation behavior showing that a decrease in Ea is accompanied by a decrease of the Arrhenius prefactor. Altogether, the system might serve as an attractive alternative to Al-stabilized (or Ga-stabilized) Li7La3Zr2O12 as LLHTO is also anticipated to be highly stable against Li metal.

Interfacial adhesion of alumina thin films over the full compositional range of ternary fcc alloy films: A combinatorial nanoindentation study

Combinatorial materials design of thin films allows one to investigate fundamental mechanic relationships and optimize films for engineering applications. Using a newly integrated shutter controller, specifically developed for precise control over coating design, ternary alloys with full compositional range can be deposited onto single wafers. Programmable shutters allow one to create multilayered thickness gradients of two or three different materials, which can then be annealed to create films with large compositional gradients. Two 50 nm fcc alloys (AlCuAu, AuAgPd) were magnetron sputtered onto (0001) sapphire wafers. The changing chemical composition across the wafer was investigated with energy dispersive x-ray spectroscopy and transmission electron microscopy. AlCuAu showed multiple phases and intermetallics across the wafer, whereas for AuAgPd a solid-solution was observed. Both alloys were coated with 400 nm Al2O3 (atomic layer deposition, ALD), to investigate their potential as adhesion layers for ALD coatings. Adhesion of the bilayers across the wafer was measured with instrumented nanoindentation, producing well-defined delamination-blisters. Small arrays of indents placed over the surface, each location corresponding to different adhesion layer compositions, illustrate adhesion-promoting properties of numerous interface compositions in single samples. For the two bilayer systems, adhesion mapping revealed the areas of optimum adhesion layer composition for best adhesion properties.

Densities and Viscosities of Binary Mixtures Containing the Polyhydric Protic Ionic Liquid(2-hydroxy-N-(2-hydroxyethyl)-N-methylethanaminium methanesulfonate) and Water or Alcohols

2-hydroxy-N-(2-hydroxyethyl)-N-methylethanaminium methanesulfonate ([BHEM][mesy]) displayed good ability for separating cellulose from biomass material in previous works. In order to have a better understanding of the structure–property relationship and facilitate further potential applications in industry, it is necessary to obtain more data for the physicochemical properties of [BHEM][mesy] and its mixtures. In this work, the densities (ρ) and viscosities (η) of [BHEM][mesy] + solvents (water, methanol, ethanol, n-propanol and isopropanol) mixtures were measured at six temperatures from (298.15 to 323.15) K over the full molar composition range and fitted by an empirical quadratic equation and Vogel–Fucher–Tammann (VFT) equation. Moreover, the excess molar volumes (VE) and viscosity deviation (Δη) of five binary mixtures were calculated and correlated by the Redlich–Kister equation. In addition, the apparent molar volumes ($${V}_{\varphi }$$) and partial molar volumes ($$\stackrel{-}{V}$$) of [BHEM][mesy] and solvents were also calculated and all these physicochemical property data (density, viscosity, excess molar properties as well as the apparent molar properties) are discussed in terms of the structure and interaction of binary mixtures.

Epitaxial growth of full range of compositions of (1 1 1) PbZr1-xTixO3 on GaN

Integrating functional complex oxides with conventional (“non-oxide”) semiconductors emerges to be an important research field and has been attracting great interest. Because of their superior intrinsic material properties, such as a relatively high dielectric constant and polarization, the utilization of PbZr1-xTixO3 (PZT) materials as a dielectric layer is expected to greatly improve the performance of the GaN high electron mobility transistor. The functional PbZr1-xTixO3 exhibits quite different crystal structures and consequently physical properties depending on the composition. In this work we report the growth of full range of compositions of PZT films on MgO buffered GaN substrates. Besides revealing the temperature effect on phase formation and surface morphology, we demonstrated the strong effect of composition on the growth: pure (1 1 1) phase is formed in Ti-rich PZT (x > 0.48) while pyrochlore impurity phase is found in Zr-rich PZT (x < 0.48). By introducing an ultrathin Ti-rich PZT seed layer, we are able to achieve epitaxial growth of Zr-rich PZT. The epitaxial PZT films of different composition all exhibit good ferroelectric properties, showing great promise for future GaN device applications.

VOLUMETRIC PROPERTIES OF ACRYLONITRILE+ETHANOL MIXTURE OVER TEMPERATURE RANGE FROM (293.15 TO 323.15) K AT AMBIENT PRESSURE

Densities of binary mixture of acrylonitrile in ethanol have been measured over the full range of compositions at temperatures from 293.15K to 323.15 K at the ambient pressure (87.9 kPa). The volumetric properties such as excess molar volumes, apparent molar volumes, partial molar volumes, excess partial molar volumes, standard partial molar volumes for binary mixture were calculated. Excess molar volumes were described by the Redlich–Kister polynomial equation. The Redlich–Kister coefficients and the standard deviations were calculated as well. The excess molar volumes exhibit mainly negative deviations from the ideal behavior over the whole range of composition for acrylonitrile+ethanol binary mixtures at low temperatures and become less negative with increasing temperature from 293.15 to 323.15 K. The results are interpreted on the basis of strong interaction between group of acrylonitrile and OH group of ethanol by hydrogen bonding. However, the sigmoid shape of plots of excess molar volumes versus molar fraction of ethanol from positive to negative values indicates to the varying interactions depending upon the composition of binary mixtures. Moreover, it is also attributed to the self-associating effect of ethanol therefore the self-associates of acrylonitrile by dipole-dipole interactions and the self-associates of ethanol by hydrogen bonding between same molecules at low concentrations predominate too.

Laser-Driven Phase Segregation and Tailoring of Compositionally Graded Microstructures in Si–Ge Nanoscale Thin Films

The ability to manipulate the composition of semiconductor alloys on demand and at nanometer-scale resolutions is a powerful tool that could be exploited to tune key properties such as the electronic band gap, mobility, and refractive index. However, existing methods to modify the composition involve altering the stoichiometry by temporal or spatial modulation of the process parameters during material growth, limiting the scalability and flexibility for device fabrication. Here, we report a laser processing method for localized tailoring of the composition in amorphous silicon-germanium (a-SiGe) nanoscale thin films on silicon substrates, postdeposition, by controlling phase segregation through the scan speed of the laser-induced molten zone. Laser-driven phase segregation at speeds adjustable from 0.1 to 100 mm s-1 allows access to previously unexplored solidification dynamics. The steady-state spatial distribution of the alloy constituents can be tuned directly by setting the laser scan speed constant to achieve indefinitely long Si1-xGex microstructures, exhibiting the full range of compositions (0 < x < 1). To illustrate the potential, we demonstrate a photodetection application by exploiting the laser-written polycrystalline SiGe microstripes, showing tunability of the optical absorption edge over a wavelength range of 200 nm. Our method can be applied to pseudobinary alloys of ternary semiconductors, metals, ceramics, and organic crystals, which have phase diagrams similar to those of SiGe alloys. This study opens a route for direct laser writing of novel devices made of alloy microstructures with tunable composition profiles, including graded-index waveguides and metasurfaces, multispectral photodetectors, full-spectrum solar cells, and lateral heterostructures.

Development of a segregation model beyond McLean based on atomistic simulations

In the present atomistic study, layer-specific segregation to the surface is investigated for an exemplary (100) surface in iron–chromium alloys using an embedded-atom potential. Through a continuous variation of the chemical potential difference in the semi-grandcanonical ensemble, the full composition range is explored at temperatures between 600 K and 1400 K. The obtained layer-specific segregation curves demonstrate the well-known limitations of the widely used McLean model for interface segregation, i.e. a monolayer model imposing ideal behavior. However, keeping the original idea of McLean, the segregation model is extended in two ways in order to provide a complete analytical description of segregation: Firstly, the entire surface is hypothetically replaced by an equivalent single layer with identical segregation properties, which accounts for all subsurface layer effects, but also enables the application of an effective monolayer model with only one single energy of segregation. Secondly, directly following from the general treatment assuming non-ideal solution behavior, the energy of segregation becomes composition-dependent. The validity and accuracy of the proposed analytical model is confirmed by fitting the composition-dependent energy of segregation to the thermodynamically unambiguous solute excess. The change in surface formation energy according to the interfacial adsorption equation can be described excellently over the entire composition range for all investigated temperatures. The model can be applied to experimental data and directly transferred to grain boundaries.

Enthalpies and elastic properties of Ni-Co binary system by ab initio calculations and an energy comparison with the CALPHAD approach

Enthalpies and elastic properties of the full composition range of Ni-Co binary system with FCC structure were investigated applying Density Functional Theory (DFT). The DFT results on enthalpy were compared with the enthalpies calculated applying the CALPHAD approach. Moreover, the effect of relaxation method, i.e. volume relaxation vs. energy-volume (E–V) curves, in DFT approach on the accuracy of the results of thermodynamic and mechanical properties were studied. It was shown that the results are very close together for the regions in which FCC is stable, but different in FCC-metastable regions. The results indicate the DFT method along with SQS approach can provide relatively reliable predictions for both energy and mechanical properties in Ni-Co system.

Realization of rocksalt Zn1−xCdxO thin films with an optical band gap above 3.0 eV by molecular beam epitaxy

We have grown Zn1−xCdxO (ZnCdO) thin films by molecular beam epitaxy on α-Al2O3(0001) substrates across the full composition range of 0 ≤x≤ 1. A large optical gap of 3.0 eV is obtained in rocksalt-ZnCdO with a low resistivity and high mobility.

Polysulfone-polyvinylpyrrolidone blend membranes as electrolytes in alkaline water electrolysis

Development of thin, dense and robust alkaline polymer membranes with high hydroxide ion conductivity is key to advanced alkaline electrolysis as it can enable operation at higher current density and/or efficiency, while improving the dynamic response of the electrolyzer. In this work, a homogeneous blend membrane system based on poly(arylene ether sulfone) (PSU) and poly(vinylpyrrolidone) (PVP) is explored as an alkaline ion-solvating polymer matrix. Increasing PVP content in the blend drastically increases electrolyte uptake, and at PVP contents higher than 45 wt%, the membrane can support ion conductivity in a technologically relevant range of 10–100 mS cm-1 or even higher when equilibrated in 20 wt% aqueous KOH. The membrane system is extensively characterized throughout the full composition range and the down-selected composition composed of 25% PSU and 75% PVP is employed in a single cell lab-scale water electrolyzer, showing excellent performance and stability during the course of one week at 500 mA cm-2 at 60 °C in 20 wt% KOH. Good performance stability was demonstrated for more than 700 h at 80 °C, but the gradually increasing KOH concentration due to evaporative loss of water resulted in membrane degradation.

The influence of water on the thermophysical properties of 1-ethyl-3-methylimidazolium acetate

Recent efforts in using ionic liquids for the dissolution of wood constituents, including cellulose, concluded that 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) is one of the most promising ionic liquids to dissolve cellulose. However, in order to make possible any industrial application, thermophysical properties of the pure liquid and of its mixtures with water are needed. In this study the influence of water on the thermophysical properties of [emim][OAc] is discussed. Density, speed of sound, viscosity, electrical conductivity, thermal conductivity, refractive index and infinite dilution diffusion coefficients were measured for mixtures of [emim][OAc] and water, in the temperature range 293.15–333.15 K, at 0.1 MPa, and full composition range. The rheological behaviour was also tested. The mixture was found to be completely miscible. Water free values for the properties of pure ionic liquid were extracted from mixture data, using new methodologies. Resultsshow that the mixture is highly structured, dominated by hydrogen bonding interactions between the water molecules and the ionic liquid acetate anions. The values of the properties establish a consistent and accurate data set for chemical plant cellulose dissolution and other future applications of these mixtures.

Nonpolar solute cononsolvency in ethanol/water mixtures – Connections to solvent structure

We present a molecular simulation study of argon cononsolvency in ethanol/water mixtures over the full range of solution compositions. First, we evaluate the solubility of argon in ethanol/water mixtures using particle insertion techniques to evaluate solute excess chemical potentials. Our simulations are in good agreement with available experimental results, importantly exhibiting a solubility minimum (excess chemical potential maximum) at intermediate ethanol concentrations at the lowest temperatures examined. Breaking the solvation free energies down into is entropic, enthalpic, and heat capacity contributions we find a distinct break between water-like and ethanol-like solvation thermodynamics at an ethanol concentration of 20 mol%. This break is accompanied with distinct changes in the solution structure suggesting argon partitions into ethanol-rich domains away from water with increasing ethanol composition. In addition, the boundary between water-like and ethanol-like solvation thermodynamics is found to lie within a concentration range in which the mixture forms bicontinuous water and ethanol clusters that span the simulation box at a nearly 50/50 vol fraction of the solvent components. We conclude with a study of the impact of cononsolvency on the association thermodynamics of argon pairs in the mixture. We find a break between water-like and ethanol-like argon interaction thermodynamics occurring at an ethanol composition of 25 mol%, similar to our solvation study. Examining the solvation shells of the two interacting argons as a function of separation, the shell is found to become progressively enriched in ethanol as the argon's come into contact. This solvation shell enrichment could subsequently provide a driving force for cononsolvency driven association/assembly.

Rheology of non-Newtonian liquid mixtures and the role of molecular chain length

We have examined mixtures of toluene, a Newtonian liquid, with several non-Newtonian liquids (i.e. surfactants) across the full composition range, from pure toluene to pure surfactant, for the purpose of exploring their rheological properties. Surfactants of similar viscosities but significantly different molecular weights were chosen, in order to verify the role of the molecular chain length. We discovered that the classical mixing rule, based on excess activation energy, succeeds for mixtures with shorter molecular chain, but fails for mixtures with longer ones. We suggest here a hypothesis which explains this difference as the result of expanding-collapsing of flexible long-chain molecules in shear flow. In order to support this hypothesis, we applied longitudinal rheology measurements which reproduce such oscillatory effects under the controlled conditions of an ultrasound longitudinal wave. This method confirms that there are qualitative differences in the rheology of these liquids mixtures with short and long molecular chains.